A device of a wheel assembly for a vehicle giving an alarm to an occupant when a tire risk judged result is “there is risk” is disclosed, for example, in Japanese Utility Model Application Publication No. Hei 4-50162 (hereinafter referred to as Patent Document 1).
A tire air pressure controller described in the Patent Document 1 has airflow rate detection means for detecting an airflow rate supplied from an air pressure source including an air pump to a tire air chamber of a wheel assembly via a stop valve to output a signal corresponding to the airflow rate; a pressure detector that detects air pressure of the tire air chamber to output a signal corresponding to the air pressure; air leakage alarming means for giving an alarm when air leakage is equal to or greater than a predetermined amount corresponding to a tire blowout based on the airflow rate detection signal of the airflow rate detection means; and a controller that opens the stop valve until a signal indicating returning of the air pressure to a normal value is outputted from the pressure detector when a signal indicating decrease in the air pressure is outputted from the pressure detector, and stops giving the alarm for a predetermined time in the early stage of the start of operation (at engine start of an automobile).
In the tire air pressure controller described in the Patent Document 1, when decrease in the air pressure of the tire air chamber is due to a large amount of air leakage such as a tire blowout, the airflow rate supplied from the air pressure source to the tire air chamber of the wheel assembly is equal to or greater than the predetermined value. The air leakage alarming means gives the alarm based on the airflow rate detection signal of the airflow rate detection means. When decrease in the air pressure of the tire air chamber is due to leaving for a long time in the state of a small amount of air leakage, upon start of the tire air pressure controller, the airflow rate is increased to give the alarm. As in the case of engine start of the automobile, the tire air pressure controller stops giving the alarm within the predetermined time in the early stage of the start of operation of the tire air pressure controller.
In the construction described in the Patent Document 1, except for the early stage of the start of operation of the tire air pressure controller, when the airflow rate supplied from the air pressure source to the tire air chamber of the wheel assembly is equal to or greater than the predetermined value, the air leakage alarming means gives the alarm based on the airflow rate detection signal of the airflow rate detection means. Regardless of the presence of risk causing large damage to the tire (tire risk), when the damage of the tire is small and the airflow rate supplied from the air pressure source to the tire air chamber of the wheel assembly is smaller than the predetermined value, the air leakage alarming means does not give the alarm so that the occupant cannot be notified of tire risk.
Such problem can be solved by setting the predetermined value to be low. In such setting, when the tire is required to be repaired immediately or the tire is not required to be repaired immediately, the air leakage alarming means gives the alarm at the time the airflow rate supplied from the air pressure source to the tire air chamber of the wheel assembly is equal to or greater than the predetermined value. Even though the tire is not required to be repaired immediately when the air leakage alarming means gives the alarm, the tire can be required to be repaired immediately by the alarm of the air leakage alarming means.